The first definitive series of Vatican stamps consists of 15 values, two of which were specifically for express mail. The seven lower values of this set depict the keys of St. Peter and the papal tiara. In 1931 these stamps were overprinted Per Pacchi for parcel post. This set is about as abundant as is the normal issue of 1931, but apparently the Vatican Post decided after that not to continue with special issues for parcel post. The first set of postage due stamps (overprinted Segnatasse) were also issued in that year.